ATLANTA — Sunday night, when the Washington Nationals needed runs to break a tied score, a relic from their past lumbered in from left field. Livan Hernandez, the man who threw the first pitch in Nationals history, the soft-tosser who started opening day last year and became obsolete this year, emerged from the Atlanta Braves’ bullpen. The carnage that followed felt like a rally wrapped inside some kind of ritual, the Nationals at once pounding the Braves and further smashing their own history into dust.

The Nationals’ lambasting of Hernandez lifted them to a 7-2 victory at Turner Field and a resounding sweep of the Braves, their first this season after nine chances. Gio Gonzalez silenced the Braves with seven electric innings, striking out 10 while allowing one lonely hit. Gonzalez bettered Brandon Beachy, the major league ERA leader, who received little help from the collapsing team around him.

The Nationals gave up a four-prospect haul for Gonzalez and signed him to a seven-year contract extension. Nine starts into his Nationals tenure, “he’s better than what I expected,” Manager Davey Johnson said.

By the time Bryce Harper came to bat against Hernandez in the eighth inning, the outcome had already been decided. There they stood, a key figure of the Nationals’ past and the most vivid symbol of their bright future. Hernandez threw Harper a 79-mph cutter down the middle. Harper unleashed his vicious swing. The ball tore a hole in the starless Southern sky. It landed seven or eight rows deep behind the right field fence. Harper sprinted around the bases.

“I was just sitting on something I could drive,” Harper said. “Livo throws really slow.”

On Memorial Day, the Nationals will wake up in first place in the National League East, 21/2 games clear of the second place New York Mets, two divisional opponents vanquished and one more on tap. On the trip that was supposed to test them, they have beaten the Philadelphia Phillies and swept the Braves. Monday afternoon, on scant sleep, they will start a three-game series against the Miami Marlins.

“We’ll be on our A game when we go down there,” Johnson said. “It’s difficult to get in at 3 o’clock when you’ve got a day game. But that’s what happens when you become a popular team. Everybody wants you on the air.”

The postgame brought an initial sigh of relief for a team already without first-string catcher Wilson Ramos for the whole season and original third-stringer Sandy Leon. Johnson called the injury “more of a mild strain” and Flores described it as “minor tightness.” Both said he would not need to go on the disabled list. Flores said he hopes to return Tuesday or Wednesday, and backup Carlos Maldonado would have caught Monday, anyway.

Sunday night, the Nationals could ease the potential issue with a nationally televised statement. Gonzalez allowed two runs in seven innings on just one hit. After a 28-pitch, two-walk first, Gonzalez made an adjustment, “trying to stay back a little bit, trying to stay tall,” he said.

After the first, he dominated. He stormed through the second in nine pitches, all strikes. The only runs he allowed came on a groundball and a suicide squeeze bunt. He retired 19 of the final 21 hitters he faced, striking out 10 of them, all of those swinging. He threw 95-mph fastballs, barely needing to sprinkle the unique curveball that ranks as one of the league’s best.

When he started throwing more curveballs at the end of his start, Gonzalez “was getting some screwy swings,” Johnson said. In the seventh, he struck out Matt Diaz swinging at a curveball that nearly hit his ankle. On his way back to the dugout, Diaz snapped his bat over his knee.

Flores said Gonzalez did not even have the same command as previous starts, and his curveball lacked sharpness, especially early. And yet, “he was still unhittable,” Flores said, laughing.

In the sixth, Gonzalez struck out the side, blowing through the first three batters in the Braves’ lineup. His pitch count climbed to 92. Gonzalez sought Johnson and told him, “Don’t you take me out. I’m going seven no matter what.”

“It still goofy Gio,” Johnson said. “But he was a little more serious than that.”

Gonzalez led off the seventh with a walk, but then struck out two more batters and walked off the mound after Jason Heyward grounded his 108th pitch to shortstop.

Gonzalez has staked an early claim to the top tier of the National League. He has a 2.04 ERA, a 7-1 record and leads the National League with 79 strikeouts. Gonzalez has allowed five or fewer hits in each of his last nine starts. In 612/3 innings, Gonzalez has yielded only 33 hits.

“Hopefully,” Harper said, “he can get a Cy Young this year.”

Sunday night, the Nationals still did not take control until the sixth inning. Danny Espinosa began the pivotal inning by taking a fastball to the triceps. It would be Beachy’s final pitch. Braves Manager Fredi Gonzalez summoned Hernandez from the bullpen, asking him to sling his slop against his former team.

The Nationals, who have scored at least five runs in six of eight games, crushed him. Hernandez would record nine outs and allow six hits. In the sixth, Flores poked the go-ahead single and Steve Lombardozzi delivered the game-breaking blow, a two-run double into the right field corner.

The Nationals piled on from there, an RBI single from Ryan Zimmerman and another hit by LaRoche. Hernandez salvaged one confrontation. He struck out Harper swinging on consecutive pitches. Harper nearly swung twice at one sinker, whiffing so hard he left his feet. Hernandez finished him off with a slow curve, which he may be able to handle with more practice at slow-pitch softball on the Mall.

“I don’t like facing guys like that,” Harper said. “I’d rather face a hard lefty or something like that. I don’t like facing slow guys. It’s not very fun.”

About half an hour later, Harper came to bat again. The Nationals had already beaten the Braves. With one last wicked swing from Harper, their present and future kicked more dirt on a piece of their past.